Taxonomy: in `get_terms()`, do not assume that legacy args are being passed when the only params are top-level `meta_*` values. Add keys in `WP_Term_Query::__construct()`.

Adds unit tests.

Props flixos90, boonebgorges.
Fixes #37568.

Built from https://develop.svn.wordpress.org/trunk@38337


git-svn-id: http://core.svn.wordpress.org/trunk@38278 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/class-wp-term-query.php

@@ -208,6 +208,10 @@ class WP_Term_Query {
 			'cache_domain'           => 'core',
 			'update_term_meta_cache' => true,
 			'meta_query'             => '',
+			'meta_key'               => '',
+			'meta_value'             => '',
+			'meta_type'              => '',
+			'meta_compare'           => '',
 		);
 
 		if ( ! empty( $query ) ) {

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.7-alpha-38336';
+$wp_version = '4.7-alpha-38337';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.